1. Field of the Invention
The present invention relates to a parking brake system for locking a brake pedal provided on a working vehicle like an agricultural or utility tractor, which has a protection system for preventing the locked brake pedal from being unintentionally unlocked.
2. Related Art
Japanese Utility Model Laid Open Gazette No. Sho 59-26060, for example, discloses a conventional parking brake system for locking pressed brake pedals. In this regard, a catch is provided on a stem of a brake pedal, and a rotatable retainer is disposed under a footboard (floor) of the vehicle so as to removably hold the catch. A parking brake operating rod interlocking with the retainer projects upwardly from the footboard. If the rod is pulled up while the brake pedal is pressed, the retainer holds the catch, thereby locking the pedal in its position. If the brake pedal is further pressed strongly then, the catch removes from the retainer, so that the pedal is unlocked.
In the conventional system, the parking brake operating rod comprises a first rod, which interlocks with the retainer, and a second rod, which serves as an operating member. A stretchable spring is interposed between the first and second rods. An outwardly biased stopper is provided on the vehicle body and the second rod is provided with a catch to be retained by the stopper. When the rods are operated to apply the parking brake, the stopper withdraws once according to the moving second rod and expands again by the biasing force so as retain the catch of the second rod. Accordingly, even if an operator alights from the vehicle while his or her foot is on the brake pedal, the brake pedal is prevented from being unintentionally unlocked because the second rod of the parking brake operating rod is retained.
However, the conventional parking brake operating rod must be pulled up to apply the parking brake against the force of the spring, thereby requiring a strong operating force. Furthermore, the operator must look into the brake pedal to determine whether the brake pedal is locked or unlocked at its position.
An object of the present invention is to provide a parking brake system which can be operated with light operational force.
To achieve the object, a first engaging member (a catch) is integrally provided on the brake pedal below a floor of the vehicle. A parking brake operating member (a parking brake lever) is disposed above the floor. The parking brake operating member is shifted so as to be retained at either a releasing position or a parking position. A second engaging member (a ratchet) for engaging with the first engaging member is pivoted on a part of the vehicle below the floor so as to be shifted between a locking position and an unlocking position according to operation of the parking brake operating member. An overcenter spring is interposed between the second engaging member and the chassis of the vehicle so as to alternately bias the second engaging member toward the locking position and the unlocking position. In such a construction, the second engaging member is retained at the locking position when the parking brake operating member is located at the parking position, and if the brake pedal is pressed at this time, engages with the first engaging member.
The parking brake system of the present invention uses a rotatable second engaging member which can be alternately biased in opposite directions by the overcenter spring. While the parking brake operating member is shifted to apply the parking brake, the second engaging member initially is biased so as to resist against the operating force on the operating member. However, when the parking brake operating member is shifted beyond a certain position, the second engaging member comes to be oppositely biased by the overcenter action of the spring so as to coincide with the operational force in direction. Then, the parking brake operating member is automatically shifted to the parking position.
Furthermore,the present invention further comprises a co-axially disposed first rod and second rod and a second spring interposed between the first and second rods so as to bias the rods toward each other, wherein the first rod interlocks with the second engaging member, and the second rod interlocks with the parking brake operating member. When the parking brake operating member is shifted from the parking position to the releasing position, if the brake pedal is not pressed, the second spring is stretched so as to allow the second rod to follow the parking brake operating member, however, the first rod and the second engaging member engaging with the first engaging member still remain, and if the brake pedal is pressed, the first engaging member is lowered so as to disengage from the second engaging member, and the second engaging member is automatically rotated to the unlocking position by biasing of the second spring through the first rod.
Accordingly, both further pressing of the brake pedal and shifting of the operating member are required to release the parking brake, thereby preventing the brake pedal from being unintentionally unlocked.
Another object of the present invention is to enable an operator sitting on a seat of the vehicle to easily decide whether the parking brake is applied or not.
To achieve the object, a grip of the parking brake operating member is provided thereon with a first caution-marked surface for indicating such a state that parking brake is released and a second caution-marked surface for indicating such a state that parking brake is applied.
The grip is disposed in relation to the seat so that, when it is located at the releasing position, only the first caution-marked surface of both caution-marked surfaces comes into view of an operator sitting on a seat of the vehicle, and when it is located at the parking position, only the second caution-marked surface comes into view of the operator.
Furthermore, the grip is vertically rotatable and the first caution-marked surface and the second caution-marked surface are extended along tangents of circles centering a fulcrum of rotation of the parking brake operating member.
The above and other related objects, features and advantages of the present invention will be apparent from the reading of the following description of the disclosure of the accompanying drawings and the novelty thereof pointed out in the appended claims.